Israel began allowing construction material for private projects into the Gaza Strip on Sunday for the first time in six years, in response to a request from Palestinian President Mahmoud Abbas, an Israeli defence official said.

Gaza, which is run by Hamas Islamists, has been struggling with a shortage of building material that has worsened since July, when the Egyptian military began a crackdown on tunnels used to smuggle goods and weapons from Egypt into the neighbouring Palestinian enclave.

The Israeli defense official said on Tuesday that 350 truckloads a week of gravel, cement and steel would be delivered to Gaza for use by private builders for the first time since Hamas took over the territory in 2007 and Israel imposed a blockade.

At Kerem Shalom, the only Israeli-operating crossing with Gaza, witnesses saw a column of trucks carrying building material enter the facility, where the cargo would be offloaded and transferred to Palestinian vehicles.

But Raed Fattouh, the West Bank-based Palestinian coordinator of supplies into Gaza, said the 70 truckloads Israel was expected to transfer each work day would fall far short of the number needed to meet construction requirements.

"Gaza is in need of up to 400 trucks of gravel, 200 trucks of cement and 100 trucks of steel every day. We have been urging the Israeli side to increase the working hours at the crossing to allow more goods to enter," Fattouh told Reuters.

Israel had said it was restricting the import of building materials to Gaza out of concern Palestinian militants would use them for fortifications and weapons.

Under international pressure, Israel began to ease the blockade in 2010 and allowed international aid agencies to bring in construction material. It further lifted some restrictions at the end of last year.

Construction has slowed in recent weeks in Gaza due to Egypt's severing of the underground smuggling lines, a sharp economic blow to a territory where the United Nations estimates unemployment has risen above 30 percent. Local assessments put the figure at 50 percent.